1. Field of the Invention
The present invention relates to a die bonding method and apparatus in which chips are successively bonded to a plurality of chip-mount portions disposed on a substrate.
2. Prior Art
In die bonding processes performed in the manufacture of semiconductors, a die bonding apparatus is used for the successive bonding of semiconductor chips to chip-mount portions such as islands, etc., that are disposed on a substrate. The chip-mount portions are disposed at a uniform pitch on the substrate; and when bonding is performed, the positional control of the driving of the bonding head is performed based on this pitch. However, there are cases in which the pitch of the chip-mount portions deviates because of the heat that is generated during bonding, etc. Accordingly, in order to improve the positional precision of bonding, the chip-mount portions for which bonding is planned is imaged before bonding, and the accurate positions of the chip-mount portions is detected based on the image data that is thus acquired.
Following the die bonding process, a die bonding inspection is performed in a separate stage by means of a spot check inspection performed by an operator or an inspection of all units performed by a monitoring camera, etc. Accordingly, since an inspection process is added following the die bonding process, there are problems in terms of the production time and human labor required. Furthermore, since there is a time difference between the die bonding process and the inspection process, there is a delay in the detection of abnormalities in cases where such abnormalities occur in the die bonding apparatus, resulting in the generation of a large quantity of defective products.
In order to solve these problems, the Japanese Patent Application Laid-Open (Kokai) No. 06-132325 discloses a die bonding apparatus in which the chip-mount portions are imaged following bonding by a camera disposed above the substrate, and a bonding inspection is thus performed. The imaging of the chip-mount portions is performed while the bonding head is moving from the substrate to the wafer and picking up chips. In this die bonding apparatus, a bonding inspection can be performed for all of the chip-mount portions immediately after the chips have been bonded. Accordingly, there is no need for an inspection process following die bonding, so that the production time can be shortened. Furthermore, abnormalities in the die bonding apparatus, etc. that cause defective bonding can be quickly discovered, so that the occurrence of bonding defects can be kept to a minimum.
However, in the above die bonding apparatus, a camera that images the chip-mount portions prior to bonding cannot be installed; and thus, detection of the bonding positions is impossible.
Here, it is conceivable to install both a position detection camera and an inspection camera. However, in the case of such a joint installation of two cameras, there is a distance between the cameras, and the chip-mount portions imaged by the respective cameras are separated from each other. Accordingly, the chip-mount portions on which bonding has just been performed cannot be imaged, and there is a possibility that a large quantity of defective units will already have been generated by the time that bonding defects are discovered by the inspection camera. Consequently, there are cases where the productivity lowers even if an inspection camera is also installed.
Furthermore, it is also conceivable to use the position detection camera as an inspection camera. However, in cases where both bonding inspection and position detection are performed, these operations must be performed while the bonding head is not located in close proximity of the substrate. This is necessary in order to prevent the visual field of the camera from being blocked by the bonding head during the imaging of the chip-mount portions for inspection purposes and the imaging of the chip-mount portions for position detection purposes. Furthermore, position detection must be completed before the next bonding operation is performed. In recent years, however, the driving speed of bonding heads has been accelerated; and thus, it is difficult in terms of time to image the chip-mount portions for inspection purposes, image the chip-mount portions for purposes of position detection, and perform image processing, while the bonding head is removed from the vicinity of the substrate. In order to accomplish this, it is necessary to stop the bonding head temporarily in a location other than the vicinity of the substrate; this, however, causes the productivity of the semiconductor products to be conspicuously lowered.